As is well known, semiconductor photo-receiving devices are semiconductor devices configured to detect light by subjecting incident light to photoelectric conversion. The semiconductor photo-receiving devices are classified into an end-face photo-receiving device configured to receive light at an end face of an optical absorption layer included in a semiconductor layer, and a surface photo-receiving device configured to receive light at a surface of the optical absorption layer.
In the end-face photo-receiving device, light enters the optical absorption layer through an end face thereof, and is scattered along a surface of the optical absorption layer. Accordingly, the light absorption efficiency of this device is high at the optical absorption layer, which means that the device exhibits a high photoelectric conversion performance. However, it is difficult for the end-face photo-receiving device to realize optical coupling with high accuracy at the end face as a photo-receiving part, which makes the structure complex.
The surface photo-receiving device comprises a substrate made of, for example, a group III-V semiconductor, a filter portion formed on the substrate and having wavelength selectivity, and a photo-detector formed on the filter portion and including an optical absorption layer. In this photo-receiving device, since light enters the photo-detector through the filter portion from the substrate side, optical coupling can be realized easily.
On the other hand, in order to receive a fast-modulated light signal, it is desirable to sufficiently reduce the photo-receiving area of the semiconductor photo-receiving device, thereby reducing its capacity.
Embodiments provide semiconductor photo-receiving devices capable of receiving light from their substrate side, and capable of increasing the absorption efficiency of incident light using an optical absorption layer of a small photo-receiving area.